Work from our laboratory demonstrated that the cytochrome P450 epoxygenases metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs). The EETs have been shown to possess potent biological activities including effects on vascular and airway smooth muscle tone, and modulation of ion transport and peptide hormone secretion. Current research in the Clinical Studies Group involves: (1) characterization of the P450 AA epoxygenase metabolic pathway at the cellular, biochemical, and molecular levels; (2) evaluation of the roles that the EETs play in cell and organ physiology; and (3) examination of this enzymatic pathway in selected human diseases (e.g. heart disease, diabetes, hypertension). Over the past year, we have cloned a new human P450 cDNA (CYP2J2) and the corresponding rat homologue (CYP2J3). Both recombinant proteins were active in the metabolism of AA to EETs. Northern analysis and protein immunoblotting revealed that CYP2J2 and CYP2J3 were highly expressed in the heart, lung, pancreas, and gastrointestinal tract. Immunohistochemistry of heart tissue sections showed that CYP2J proteins were primarily expressed in cardiac myocytes and at lower levels in cardiac endothelial cells. In the lung, CYP2J proteins were expressed in ciliated and non-ciliated airway epithelial cells, pulmonary vascular and bronchial smooth muscle cells, vascular endothelial cells, and alveolar macrophages. In the pancreas, CYP2J proteins were highly localized to alpha- and beta-cells of the islets of Langerhans. In the intestinal tract, CYP2J proteins were expressed in epithelial cells, nerve cells of autonomic ganglion, and smooth muscle cells. The in vivo significance of CYP2J proteins was confirmed by demonstrating, for the first time, the presence of EETs in heart, lung, pancreas, and intestine using gas chromatography/mass spectroscopy. Synthetic EETs were shown to protect the heart against the functional consequences of global ischemia and inhibit chloride secretion in cultured airway epithelial cells. Future work will focus on the following: (2) the regulation of CYP2J2 and CYP2J3 gene expression; and (b) functional significance of CYP2J products in pulmonary, cardiac, pancreatic and intestinal function.